This invention concerns a crystallizer, or inner portion, of a mould having a lengthwise continuous curvature for the continuous curved casting of thin slabs.
The invention concerns, in particular, crystallizers of moulds with upper lenticular enlargements and a continuous lengthwise curvature, the moulds being suitable for the continuous curved casting of thin slabs.
The invention can be applied to moulds having a single lengthwise curvature or a multiple lengthwise curvature.
"Lengthwise" here means in the direction of feed of the solidifying molten metal.
Document US-A-2,564,723 discloses a crystallizer for linear moulds for the continuous casting of thin slabs by making use of lenticular enlargements in the long walls of the mould. This document teaches the symmetrical enlargement of a straight vertical crystallizer and is not suitable for curved crystallizers.
US-A-4,134,441 discloses adjustable lateral narrow sidewalls for use in crystallizers of linear moulds for the casting of slabs. These sidewalls have a tapered development such that they narrow the channel of the steel progressively as that channel is distanced from the meniscus of the liquid metal towards the outlet of the mould.
DE-A-3.528.649 discloses a crystallizer of a linear mould with its upper portion formed as a funnel and with substantially linear sides.
EP-A-0230886 is associated with a vertical straight crystallizer containing a symmetrical enlargement, which has inclined vertical walls with a substantially rectangular development.
DE-A-3.501.422, EP-A-0149724 and DE-A-3.907.351 too disclose a vertical straight crystallizer with a symmetrical enlargement.
EP-A-0300953 discloses a crystallizer which is straight and vertical in its upper portion where the tundish discharge nozzle is inserted, whereas its lower portion is curved. The crystallizer can also include in its upper portion an arcuate segment which may be on one long side or the other, but no geometric parameter of definition is disclosed. It does not in any way provide for the case of a wholly curved crystallizer and envisages a change of direction of the skin of the thin slab being formed. This change of direction takes place where the straight vertical segment is joined to the lower curved segment and creates problems for the skin being formed, with separations, discontinuous surfaces, localized melting and reduction of withdrawal speeds.
With the technology of the state of the art the steel during continuous casting with partly curved moulds of a known type undergoes dynamic effects due to the motion of withdrawal and the shrinkage due to cooling.
EP-A-027 6418 and JP-A-5897466 include lateral elements for closure and determination of the length of the casting chamber; the former document discloses straight vertical crystallizers, whereas the latter discloses curved crystallizers.
No document of the state of the art concerns a wholly curved crystallizer of a curved mould with both its longer walls including an upper lenticular enlargement, such a mould being curved and suitable for the continuous casting of thin slabs.